Identification of feline erythrocyte antigen 6 and lack of alloimmunization to feline erythrocyte antigen 4 in cats

Abstract

Background

New feline erythrocyte antigens (FEAs) have been described based on the presence of naturally occurring alloantibodies (NOAb), but their immunogenicity and clinical relevance are poorly understood.

Hypothesis/Objectives

Describe the immunogenicity of FEA 4 after sensitizing FEA 4–negative cats lacking NOAb and characterize anti–FEA 4 alloantibodies produced, including their rate of appearance, agglutination titer, and immunoglobulin class.

Animals

Nineteen healthy type A cats were blood typed for FEAs 1 to 5 to identify suitable donor-recipient pairs for FEA 4 sensitization.

Methods

Four FEA 4–negative cats were transfused with FEA 4–positive red blood cells. Using a gel column technique, posttransfusion samples were screened daily for a week, weekly for a month, and monthly thereafter for anti–FEA 4 alloantibodies.

Results

Alloantibodies were not detected in the first 3 recipients despite repeated transfusions (1 and 3 additional transfusions for 2 and 1 recipients, respectively). In the 4th recipient, alloantibodies against its donor red blood cells were detected 21 days postsensitization. However, they were not directed against FEA 4, but rather against a novel FEA not yet described. The alloantibodies, named anti–FEA 6, remained detectable for >4 months after sensitization and were determined to be mostly immunoglobulin M based on sulfhydryl treatment.

Conclusions and Clinical Importance

Feline erythrocyte antigen 4 does not appear to be immunogenic because repeated sensitization of 4 cats failed to produce detectable anti–FEA 4 alloantibodies. A new immunogenic antigen, named FEA 6, has been discovered, but additional studies are needed to document its clinical importance.